Surviving 7.8: Life after the Kaikoura earthquake

Just after midnight on November 14 last year the world’s second most powerful quake of 2016 struck under the North Canterbury hills. The Herald on Sunday has an extract from a new book that explores the drama, the scientific puzzle and the human spirit of the people who live there.

The full power of the Kaikoura quake is demonstrated in the massive ruptures in the land. Photo / Kate Pedley

To appreciate the enormous power unleashed by such an earthquake, you need only to look out Jacqui Hamilton’s window over the land stretching 10km down the Clarence River valley towards the sea.

With a photo to hand, you can compare what you see now with what there used to be, on November 13.

“The bridge is lying in the river, yes,” says Jacqui, who raised her children here for 21 years and now lives alone on a 4ha block.

“We had a lot of uplift and a lot of land damage up the valley.

“Apparently, we live on a fault line and that fault line ruptured. I was talking to one of the geologists, and she said the fault that ran under our houses was only a fault they suspected was there.

“It is totally surreal: you go to bed at night and the landscape is as you’ve known it for 21 years – and the next morning it has changed out of sight.”

She laughs. The difference?

“Oh, I can actually see the Clarence now. I couldn’t see the Clarence before ‘cos it was running low.

“So I’m higher. My land was all flat and now it’s undulating and fractured; it’s got terraces everywhere, my garden’s all full of terraces and great big splits.

“Some parts of the land have come up, some parts have gone down, and at the Clarence itself, it’s a lake rather than a flowing river. I mean it’s still flowing, but there’s a great pool of water there about 6km back up the river.”

Every earthquake is unique, but the Kaikoura one is off the charts for its complexity and the puzzles it’s now presenting to a whole raft of scientists.

They need to unravel its secrets, to understand more about why and how the Earth moves – and when it might happen again.

On GeoNet’s website, a map of the top of the South Island lets you watch the rupture march up the east coast as it triggers seismic sensors first at Hanmer Springs, then at Kaikoura, then Molesworth, Kekerengu, Ward, Seddon.

Scientists inspect fault damage around Waiau. Photo / Kate Pedley

Some of these sensors had been rolled out across Canterbury and Marlborough only since 2010, in a $45 million GNS – Earthquake Commission programme aimed at placing 30 new seismic stations and 16 GPS sites in the Marlborough fault zone.

One minute and one second in, it’s recorded as only a 6.5 magnitude – “only”, although the wrecking ball that was the February 2011 Christchurch quake was just 6.3, but shallow and located right under the city.

Two minutes on from the initial hit, the recorded magnitude rises to 7.

It’s not until Wednesday evening, just after 6pm, that enough data have been crunched from both the sensors close at hand and those more distant to declare the quake a 7.8 – which means it has released 89 times more energy than a 6.5.

A geological shuffle of this magnitude leaves its mark.

From space, Japanese and European radar satellites that measure the distance to the ground incredibly accurately – and so can spot any shifts – confirm the quake has caused massive permanent displacement of the land in the northern half of the South Island.

Nasa releases images from its Earth Observatory that show new land thrusting out into the sea. The biggest shifts are across the Hope and Kekerengu, and the Hundalee and Papatea faults.

To the east of these faults, the land has shifted mostly southwest; to the west, it has moved mostly northeast. GNS computer simulations suggest at some points on the Kekerengu Fault north of Kaikoura, the land has done a radical, 10m sideways slide either side of the fault line.

Dust created by a strong after-shock hangs above the Clarence River. Photo / Mark Mitchell

It shifted in just a few seconds.

Clarence farmer Julia says they heard the water being tossed sideways out of their concrete swimming pool, and at the same time it was like going upwards, quickly, in a lift.

She has been told they were subjected to three Gs of force.

What’s more, according to GeoNet, this is one of the most complex earthquakes ever observed – in the same league as the 1855 Wairarapa earthquake and the catastrophic 1906 San Francisco earthquake that travelled over hundreds of kilometres of the San Andreas Fault.

One puzzle is why the Hope Fault, which links the Alpine Fault to the ones that ruptured, has hardly moved at all.

The mysteries of fault lines are myriad. GNS senior scientist Russ Van Dissen knows this much, although he also knows the Kekerengu Fault better than most.

At one point he stands inside a chasm twice his height, pulled apart on a farm near Ward.

“It looks like a big, huge ploughshare has just gone screaming across the landscape from as far as we can see in one direction to as far as we can see in the other direction,” he says.

“It’s not often you see a fault that ruptures by up to 10m. Fissures in the ground are common, but the size of these are uncommon because this displacement is way bigger than common.”

It looks like a big, huge ploughshare has just gone screaming across the landscape.

Russ Van Dissen

At another spot, the split dirt crack of the fault sweeps unbroken around a small hillside, like a thick trail of oil left on a banked race track.

Initially, it’s thought six faults ruptured at 12.02am, with a combined jolt equivalent, some say, to 400 atomic bombs.

Then the number goes to seven, and by early December GNS has updated this to 12, including the Fidget Fault and the newly named Uwerau Fault.

Appreciation of what has occurred is immediate but understanding comes gradually, in fits and starts, as the experts drill down through the evidence.

“This particular rupture has let the cat out of the bag in some respects, because it has ruptured a series of faults that we wouldn’t have thought would rupture together in an earthquake of this magnitude,” GNS’s Jamie Howarth says.

“That has implications for how we go about modelling seismic hazard in this country.”

Russ Van Dissen sees it as confirming a theory they had been working on.

“When we pieced the story together and actually got the results back, we identified three big ruptures in the last 1200 years.

“So in the last thousand-ish years, this fault has ruptured three times – and now it’s the fourth time.

“Four hundred years sounds like a long time to humans, but as far as the fault lines go it’s one of the most active in New Zealand.”

Dr Kate Pedley, of University of Canterbury’s Department of Geological Sciences, shared on Facebook some of the dramatic sights. Photo / Kate Pedley

The way the sea behaved carries its own mysteries. Many people have wondered out loud whether Civil Defence was crying wolf with its tsunami alert.

No way, according to Helen Jack, a geological hazard analyst at GNS.

“The earthquake triggered a tsunami, and if it hadn’t been for the substantial coastal uplift in many places, and the low tide at the time, it could have been much more damaging,” she says in a blog post.

“Currently the only report of the tsunami impacting property was at Little Pigeon Bay on Banks Peninsula, where a house was badly damaged. However, there are numerous reports of the sea leaving seaweed, shellfish and fish stranded above high-tide level.

“There are also observations of the sea level falling below low tide, rising and falling quickly, and strange surges and currents.”

At the Clarence River Rafting company base, admin person Jacqui Hamilton is champing at the bit.

She can’t get to her home up the valley because the Glen Alton bridge over the Clarence River fell down at 12.02am; and she can’t get to her other job, two days a week down at a school in Hapuku, because the state highway is blocked.

She has friends in the same boat, people who can’t get to their jobs in a town that was once a 30-minute drive away.

One works at the supermarket, another at the district council, and another drives a bus. Jacqui’s home, along with seven or eight others, is to all intents and purposes cut off from anyone without a high-riding four-wheel-drive and nerves of steel.

“They have put in a temporary four-wheel-drive track up the south side through the Wharekiri and Miller streams and then through private property, so we can get in, but you have to have a four-wheel-drive, you have to have a high-clearance vehicle, because the Wharekiri runs quite deeply, quite swift and scours out quite quickly.

“So for me, I don’t … at the moment I’m kind of stuck.”

The quake has caused massive displacement of the South Island.

Jacqui’s neighbour, trophy-hunt operator Steve Millard, doesn’t blame her for avoiding the road. He has bulldozed it, but the clay is slippery in the wet, and he has butted heads with the district council over putting down gravel.

Jacqui asks him to sign her letter to the council protesting at how little information locals have had, both about the valley road and about State Highway I to Kaikoura, and about when – or even if – they’ll be fixed.

When every day new stories are appearing about the demolition of Wellington’s buildings and the slip-clearing on the highway south of Kaikoura, it’s just a little galling.

Jacqui says it’s ridiculous she has to write a letter from inside an emergency zone to find out what’s going on.

She remains in good humour, though that won’t stop her doing something about the matter. She’ll send off the letter; maybe she’ll even buy herself a four-wheel-drive.

She laughs. Maybe that’s not such an outlandish thought.

The two sides of a coin flip and flip and flip again in the stories we are told: there are a lot of downsides, like Jacqui’s, but then along comes an upside.

The downsides can provide impetus: maybe Jacqui will look back on this as the time she got that high-riding four-wheel-drive that opened up the hinterland for her and steeled her nerves?

Although the upsides are far fewer, they are all the more special for that: people seize on them, they lift their spirits.